There has been developed a conventional optical fiber cord as shown in FIG. 1. The conventional optical fiber cord shown in FIG. 1 is provided with a tape core type coated fiber 1, a reinforcing member 12, a reinforcing sheath 13, a single fiber 4, a branching portion protecting plate 15, a reinforcing housing 17, a resin 16, and an optical fiber connector 7. The tape core type coated fiber 1 is adhered to the branching portion protecting plate 15.
Further, there is another conventional coated optical fiber branching portion of a five-to-one fiber conversion cord shown in 1988-Spring National Meeting B-599 of the Institute of Electronics, Information and Communication Engineers of Japan.
According to the conventional optical fiber cord shown in FIG. 1, the tape core type coated fiber 1 branching on the branching portion protecting plate 15 is provisionally fixed to the branching portion protecting plate 15 through an adhesive, and then, each of the tape core type coated fiber 1 and the single fibers 4 is coated with the reinforcing sheath 13, an end of the sheath 13 and the connection portion between the tape core type coated fiber 1 and the single fibers 4 are covered with the reinforcing housing 17, and the resin 16 is filled in the reinforcing housing 17. Such an optical fiber cord would cause a drawback that stress is exerted onto the tape core type coated fiber 1 and the single fibers 4 in filling the resin and in hardening the resin to thereby increase undesirable light transmission loss.
Further, the conventional optical fiber cord would suffer from a problem that the tape core type coated fiber 1 and the single fibers 4 are subject to stress by thermal expansion of the resin 16 when an environmental temperature varies since they are molded with the resin 16, so that the light transmission loss may increase.
Moreover, there would be raised a further problem that the work for fixing the branching portion of the tape core type coated fiber 1 to the protecting plate 15 is fine work and poor in workability and, therefore, the light transmission loss may increase if the setting is not well.
There has been a still further problem that since the branching portion has such a basic configuration as described above, it is necessary to provide the protecting plate 15 when the tape core type coated fiber 1 is branched into the single fibers 4, and it is impossible to provide a mere branching portion of the single fibers 4 of the tape core type coated fiber 1.